350MW超临界缝隙式W火焰锅炉炉内单相流动特性试验研究

发布时间：2018-10-21 11:10

【摘要】：我国目前的W火焰锅炉燃烧技术均是从国外引进，哈尔滨工业大学在对四个主要W火焰锅炉燃烧技术深入研究后提出了“多次引射分级燃烧技术”，该技术在工业示范后取得了不错的成果，，作为我国具有自主知识产权的Ｗ火焰锅炉燃烧技术有着较高的研究价值。本文以一台350MW超临界W火焰锅炉作为研究对象，以其为原型搭建了1:13的冷态模化试验台。在试验台上进行烟雾示踪试验优化燃烧器喷口布置方式，还利用热线风速仪测量炉内的空气动力场，试验研究得到以下结论：当乏气喷口前置时，一次风气流不对称，乏气气流在炉膛深度方向剧烈摆动，且出现了严重短路现象，炉内流场不够稳定，将乏气风速提高以后，流场没有明显改善。当乏气与一次风集中布置时，拱上气流没有出现短路现象，拱上乏气和一次风气流较稳定，前后墙气流对称分布，但是气流的刚性较强，下射深度大，有可能会冲刷冷灰斗。当一次风、乏气间隔布置时，炉内的拱上气流对称性和稳定性都较好，下冲深度合适，没有冲刷冷灰斗的现象。综合考虑采用多次引射分级引射燃烧理念的一次风、乏气间隔排列的燃烧器布置是较为合理的。通过二次风和三次风风量配比的冷态调整试验可以发现，在前后墙三次风水平喷入炉膛内的情况下，炉内流场极易出现偏斜，在二次风风率为15%和25%时，炉内的流场在冷灰斗拐角上部区域以及冷灰斗区域都是偏斜的，后墙气流占据主导地位，对W火焰锅炉的燃烧和安全运行是极其不利的；增大二次风风率到28.35%时可以减轻流场的偏斜，只在冷灰斗区域出现轻微流场偏斜；当二次风风率增大到35%时，流场偏斜基本消除。通过三次风下倾工况下的炉内空气动力场试验表明，三次风下倾角度为0o时下炉膛流场呈现明显的不对称性，后墙侧的气流占据了主导地位，将使前墙侧煤粉气流燃烧行程变短，煤粉在炉内停留时间短，飞灰含碳量升高，从而降低了锅炉效率；当三次风下倾角度为20o和30o时，炉内呈现出规则的W型流场，前后墙侧气流在下行过程中遇到三次风，两股气流混合后继续下行一段到冷灰斗中部位置后转折上行，延长了煤粉颗粒的燃尽行程，这对提高锅炉效率是有利的。从炉内水平截面的速度分布来看，三次风下倾角度为20o的工况速度的对称性好于三次风下倾角度为30o的工况，因此建议三次风下倾角度为20o。
[Abstract]:At present, the combustion technology of W-flame boiler in China is imported from abroad. Harbin University of Technology has put forward the "multi-ejection staged combustion technology" after deeply studying the combustion technology of four main W-flame boilers. The technology has achieved good results after industrial demonstration. As a W flame boiler combustion technology with independent intellectual property rights in China, it has high research value. In this paper, a 350MW supercritical W flame boiler is taken as the research object, and the 1:13 cold model test bench is built with it as the prototype. The smoke tracer test was carried out on the test bench to optimize the burner nozzle layout, and the aerodynamic field in the furnace was measured by using a hot wire anemometer. The primary air flow is asymmetrical, and the flow field is not stable enough because of the severe short circuit and the sharp swing of the air flow in the furnace depth. The flow field does not improve obviously after the increase of the air velocity of the spent gas. There is no short circuit in the air flow on the arch when the air is concentrated with the primary air, the air flow on the arch is stable and the air flow on the front and back wall is symmetrical, but the air flow is more rigid and the depth of the downfire is large, so the cold ash bucket may be washed away. When the primary air and the spent air interval are arranged, the airflow symmetry and stability of the arch in the furnace are better, the depth of the downflow is suitable, and there is no phenomenon of scouring the cold ash bucket. Considering the primary air with multiple ejection stages, the arrangement of burner with spent gas interval is reasonable. Through the cold state adjustment test of the ratio of secondary air and tertiary air volume, it can be found that the flow field in the furnace is prone to skew when the horizontal air of the front and rear walls is injected into the furnace, and the secondary air rate is 15% and 25%, respectively. The flow field in the furnace is skewed in the upper area of the corner of the cold ash hopper and the area of the cold ash bucket, and the air flow on the back wall occupies the dominant position, which is extremely unfavorable to the combustion and safe operation of the W-flame boiler. When the secondary air rate is increased to 28.35, the deflection of the flow field can be alleviated, only a slight deflection of the flow field appears in the area of the cool ash hopper, and when the secondary air rate increases to 35, the deflection of the flow field is basically eliminated. The experimental results of aerodynamic field in the furnace under the condition of triple-air downdip show that the flow field of the furnace shows obvious asymmetry when the downdip angle of the third air is 0 o, and the airflow on the back wall occupies the dominant position. The combustion stroke of pulverized coal flow on the front wall side will be shortened, the residence time of pulverized coal in the furnace will be shorter, the carbon content of fly ash will be increased, and the boiler efficiency will be reduced. When the downdip angle of the third air is 20 o and 30 o, the regular W-shaped flow field will appear in the furnace. The front and rear wall side air encountered three times air in the downgoing process, and the two airflow mixing continued to the middle of the cold ash bucket and then turned upward, which prolonged the burnout stroke of pulverized coal particles, which was beneficial to improve the boiler efficiency. According to the velocity distribution of horizontal section in the furnace, the symmetry of the velocity of the third air downdip angle is better than that of the third air downdip angle of 30 o, so it is suggested that the third air downdip angle should be 20 o.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TK229.2;TK226.1

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